1. Field of the Invention
The present invention relates to communications systems, and more particularly to microfilm systems in which data is stored in digital and/or graphic form on a circular storage media, such as microfilm, thermoplastics or paper, and is optically scanned by light transmission, light reflection or light refraction apparatus.
2. Description of the Prior Art
In Gokey et al Ser. No. 922,798, filed July 7, 1978 and Gokey et al Ser. No. 956,426, filed Oct. 31, 1978, a microfiche system is disclosed in which a microfiche card bears digitally encoded information and is read by an optical scanner which indexes the card to a desired address and optically scans the data content at that address. Also disclosed in these applications is a viewer microfiche, bearing graphic information (including drawings, alphanumeric, etc, other than digital information) which is addressed by digital codes for viewing on a screen. Each of the microfiche, both the digital microfiche and the viewer microfiche, were provided with indicia to correct for skew and to provide tracking alignment.
Murakoshi, in his U.S. Pat. No. 3,792,440, discloses a film disc memory which photographically stores clock signals in the radial direction and index signals in the circular direction to control the x-y movement of a microfiche transport to properly position a desired frame in the light path of a viewer.